Local survival rates of the pied flycatchers (Ficedula hypoleuca) and the great tits (Parus major) in an air pollution gradient

Abstract

We studied the local survival of pied flycatcher (Ficedula hypoleuca) and great tit (Parus major) females under heavy air pollution stress. Females were trapped from three distance zones around a copper smelter in the town of Harjavalta, southwestern Finland, from 1991 to 1995. The main pollutants in this area are heavy metals (Cu, Ni, Zn, Pb) and sulphuric oxides. Local survival rate (affected by mortality + emigration) was estimated in three distance zones using capture-recapture models. Survival and recapture probabilities were separately estimated from breeding to next breeding for F. hypoleuca and by half year trapping periods for P. major. The local survival rate of F. hypoleuca females showed a decreasing, although marginally significant, trend towards the polluted area. No indication of such an effect was found in P. major. Immigrant breeders formed about 89% of the population of F. hypoleuca females in our study area. Possible reasons for the low survival rate in F. hypoleuca are discussed. We suggest that the low local survival rate of F. hypoleuca females is caused by higher emigration from the low quality and unproductive habitat rather than by the direct mortality of adult birds due to heavy metals. Better wintering conditions next to the human inhabitation may compensate for the possible detrimental effects of pollutants on the P. major population.